bpf: pfc: Add handling for 0 syscalls in the binary tree

Handle the unlikely case where a user has chosen the
binary tree optimization but has zero syscalls in their
filter.

Fixes: #370
Fixes: a3732b3 ("bpf:pfc: Add optimization option to use a binary tree")
Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>
Acked-by: Paul Moore <paul@paul-moore.com>

src/gen_bpf.c

@@ -1348,6 +1348,9 @@ static int _get_bintree_levels(unsigned int syscall_cnt)
 {
 	unsigned int i = 2, max_level = SYSCALLS_PER_NODE * 2;
 
+	if (syscall_cnt == 0)
+		return 0;
+
 	while (max_level < syscall_cnt) {
 		max_level <<= 1;
 		i++;

src/gen_pfc.c

@@ -275,6 +275,9 @@ static int _get_bintree_levels(unsigned int syscall_cnt,
 		/* Only use a binary tree if requested */
 		return 0;
 
+	if (syscall_cnt == 0)
+		return 0;
+
 	do {
 		max_level = SYSCALLS_PER_NODE << i;
 		i++;